Methods useful in treating earth formations



United States Patent Ofifice 3,136,369 Patented June 9, 1964 3,136,360 METHODS USEFUL IN TREATING EARTH FORMATIGNS Joe Ramos and Home: C. McLaughlin, In, Duncan, 01:12., assignors to Haliihnrton Company, a corporation of Delaware No Drawing. Filed Apr. 25, 1960, Ser. No. 24,227 11 Claims. (Cl. 166--12) This invention relates to the treating of earth formations to control the flow of fluid into and through pore spaces and other openings providing fiuid passageways therein. More particularly, the invention relates to compositions and methods useful in sealing-off a permeable zone or section of an earth formation, such as a formation penetrated by the bore of an oil or gas well or the like, and further relates to controlling the injection of sealing or seal-forming compositions into the permeable formations to be treated.

The present application is a continuation-in-part of copending United States application Serial No. 711,153, which was filed on January 27, 1958, and is now abandoned.

It is anticipated that the invention will be applied most widely in connection with treating operations performed for the purpose of sealing-off earth formations into which it is relatively difficult to inject sealing compositions. One application wherein the invention provides particular advantages is in connection with the sealing-ofi of underground water-bearing formations in Wells being drilled by the air or gas driling method.

The technique of air or gas drilling differs from conventional drilling techniques mainly in that air or gas is used instead of a drilling liquid for the purpose of removing the cuttings from the bore hole. By the use of air or gas, the cuttings are discharged in the form of a dust or powder, rather than as part of a liquid stream.

As long as no water zones are encountered the air or gas drilling method has many advantages. However, it is very infrequent that water zones are not encountered. When the drill bit penetrates a water zone, the water flows into the bore hole with obvious disadvantages. The air or gas pressure is not sufficient to blow any appreciable quantities of water out of the bore hole. The water will wet the cuttings, which results in a sticky mass which cannot be blown out of the bore by the air or gas. In addition, the wetted cuttings tend'to clog the drill bit and cling to the walls of the well bore. In many instances the drill bit and drill pipe becomes firmly stuck in the bore hole.

Since the advent of air and gas drilling, the undesirable production of water has been the major drawback to its universal application. As a result, extensive efforts have been devoted to the solution of the problem of shutting off the flow of Water into the bore hole.'

A suggested method for sealing a porous formation is described in United States'Patent No. 2,801,98410 Morgan and Padb ury, issued August 6, 1957. In accordance with this patent, a copolyrner mixture is injected into the porous formation, and by reacting with the soil of the formation converts the compositionin situ to a water-insoluble state, thus, sealing the porous formation. However, applicants attempts to apply this method in shutting off flowing water were unsuccessful. It was discovered that a formation which produces water has entirely different characteristics from a non-producing porous formation which obviously will readily receive liquids. For example, in attempting to pump thickened liquids into a water producing zone, it was found that a fracture was inevitably created. In the oil well art it is well known that the creation of fractures increases production from the fractured zone. Therefore,

such fractures of a water-producing zone increase the water flow instead of reducing it. I

Another major problem heretofore encountered has been the difiiculty of controlling the time of gelation of the sealing composition used in treating an underground earth formation. It is desirable to avoid premature gelation, such as may occur while the composition is in the well conduit prior to reaching the formation to be treated. This occurrence has at times resulted in an unsuccessful operation which was time consuming and costly.

Even where the time of gelation may be successfully controlled, however, it has been found difficult in many instances to inject the sealing composition in sufiicient quantities at the desired location and for the desired dis tance into the earth formation to obtain a successful shut-off of the water. This is particularly the case where the sealing composition contains colloidal or other particles which tend to clog the pore spaces and other openings in the formation and, in this way, reduce or obstruct the entry of the sealing composition into the formation in the required amounts.

A general object of the present invention is to provide improved compositions and methods useful in treating earth formations to control the flow of fluid in passageways therein.

Another object of the invention is to provide improved treating compositions for use in wells and to provide an improved well treating method wherein such compositions are utilized in sealing-off or substantially closing passageways in the underground strata penetrated by the bore of the well.

Another object of the invention is to provide an improved treating composition and an improved method utilizing the same in treating an underground water-bearing formation.

A further and more specific object of the invention is to provide an improved treating composition and an improved method utilizing the same in sealing-off an underground water-bearing formation penetrated by the bore of a well in which air or gas drilling operations are being performed.

In accordance with the invention, the foregoing and additional objects and advantages are attained by uti: lizing a fluid-treating composition having sealing or sealforming properties and containing an additive in the form of a filter aid material which increases the fluid loss properties of the composition during the injection thereof into an earth formatiomsuch as intoan underground water-bearing formation penetrated by the bore of a well.

As used herein, the term .filter aid material includes material in the form of finely divided, water inert solid particles having suitable surfaces, 'such as irregular 'and/ or porous surfaces, which permit the particles to be accumulated into permeable deposits, such as into layers forming a permeable filter cake. Examples of materials which may be successfully employed are the synthetic calcium silicate compounds which are commercially available from Iohns-Manville under the names Micro- Cel A, Micro-Gel B, Micro-Gel C, and Micro-Col E. Other examples are the diatomaceous silica materails which are commercially available, for example,-from a two-shot system, such as where sodium silicate solution and a gelling agent therefor are separately introduced into the well and then allowed to come together at a desired natively, the sodium silicate gels may be employed in a one-shot system, such as where an indirect or delayed fate, commonly called Hypo, is an exa mple of a suitable location in or opposite theformation to be treated. Alteracting gelling agent is included with the sodium silicate solution introduced into the well. See the co-pending United States application Serial No. 22,681 "filed by Homer McLaughlin, Jr., one of the inventors herein.

In another way of proceeding, thetreating composition is prepared bycombining a filter aid material with a polymerizable mixture capable in time of forming a gelled mass. 7 d

The polymerizable mixture may, for example, be a mixture of95% acrylamide and 5% N,N' methylene, bisacrylamidetogether with a suitable catalyst, such as ammonium persulphate, as taught in United States Patent No.. 2,801,985 to Roth. This mi'xtureis capable of gelling inwater, such as after mixing with water in the permeable zone or formation to be treated. It is emphasized that the polymerizable mixture, which is employed in conjunction with other chemicals, results in a gelled mass after a period of time and no reliance is made upon any reaction of the materials with the soil in the formation. This mixture is placed opposite a pumped down a metallicwell conduit, a corrosioninhibitor should be included.

Another factor to be considered in usingthe acrylamide and N,N methylene bisacrylamide solution, with the cat: alyst added, is the effect: of the pH of the solution on the rate of gelation. At a veryhigh orvery low 'pH the gel time is indeterminate and the strength diminishes rapidly.

might gel at any time. Therefore, a salt which will. controlthe pH is required. The preferred pH of the solution'is 8. However, a pH in the range of 7 0.1211128 been foundt'o be satisfactory. a

Under theseconditions, no control could be exercised in placing the solution in a well bore, as it Thus, a solution of acrylamide and N,N. methylene bis:

acrylamide, a catalyst, a corrosion inhibitor, and a salt to control the pH of the solution provide a composition which may be employed'in shutting off a water producing formation. However, it has been discovered that temperature conditions affect the time of gelation, and indiscriminatefmixing of the above substances. results in a solution which is not controllable as to time. of gelation or viscosity; In particular, it has been found that the dry ingredients should be added to the water in a prescribed sequence. In addition, different proportions are requiredfo'r various temperature ranges. j

Where this polymerizable mixture is employed, the following with continuous mixing of the ingredients:

is the preferred sequence of steps to befollowed,

(1) Add disodium phosphate duohydrate (DP D to. Q l

the water. This is a salt which controls the pH of the'final solution. a V v (2)" Add a polymerizable mixture comprising about acrylamide and 5% N,N' methylene bisacrylamide.

This is the basic gelling material.

. 3) Add potassium ferricyanide (KP). This is the corrosion inhibitor to prevent flashsetting.

(4) Add the filter aid material, such as a purified di-' atomaceous silica filter powder of medium size. This aids the final solution in penetrating the formation;

2. Micro-Gel O 10 319 m1.30 min. 3.; d0 j 5 410 ml.30min. L- -do.-- 2. 5 528 TELL-29.5 min. 5* .410". 2 550 m1.-24 min. 5 (10 1.5 490 n1l 30 min. 7 do- 1' 330 m1..30 min.

. s Micro-Gel 2 552 ml.30 min. 9 M1cro Cel E 2 293 ml.30 min. 10- Micro-Gel A 2 540'm1.-7.5 min. 11 d0- 2 558 ml.10.5 min. 12- d0 1. 5 558 Inl.--18.6 min. 13 d0- 1 372 ml.30 min. 14". Filter-Ce1 '1 160 rah-30 min. 15. Celite 512 1 365 ml.--l.75 min. 16- o 1.5 560 ml.3.1 mini 17- Hyflo Super 0.75 502 ml.12.1 min; 18- do 1 370 ml.1 min. l9 .110- :1. 5 550 ml.-'-2.3 min. 20- d0 3 560 ml.1.67 min. 21--. Celite 503 1 370 ml.4.25 min. 2 2 d0'. 1. 5 336.m l. -30 min.

- In order to treat a-water producing fOImBIIQII 1n abore booster. The booster is only required at the lower. tem peratures. V w i I f ;(6) Finally, add the catalyst, such as ammonium persulphate (AP). I,

' (7) Continue to mix thesolution forapproximately 5 minutes. V p

The resulting solution has a viscosity about the same as water and will not gel until the times shown in the table below elapse.

In order to compensate for the different temperature I conditions, the percentages of materials in the table below should be used. However, some variations are permissible. In the following table a solution'of' acrylamide and N,N methylene bi'sa'crylamide in waterlis'pre'pared by mixing 10 parts acrylamide' and N,-N methylene with '90 parts: of water, by weight', with 2 percent DPD added.

c a Gel Gel 4 Hypo, AP, KF, Time, 1Tirne, Temp. Range, F. percent percent percent Low High Temp., Temp,

' min. min;

0.5 a 1.0 0.02 87' .45 0. 5 0. 5 0. 0'1 88 52 None 0.5 0.04 95 48 None 0. 2 0. 08 .105 75 None 0.2 0.12 107 v 64 None 0.2 0.16 .48 None 0. 2 0; 18 53 40 1 Actual pumping or grouting time. 7 I c In yet another way. of proceeding, also in accordance with the invention,the treatingcomposition isjprepared V by combining 'a' filter aid material with one'or more of the ingredients used in preparing a chrome lignin gel.

For example, the treating composition may be a chrome lignin gel prepared by combining grams of lignin liquor. (clarion extract 96 milliliters of'water and 5.2

grains ofchromic acid, with the filter aid material being added to. one or more of the ingredients and, in any event,

being preferably uniformly dispersed inthe final mixture.

, Laboratory tests have been conductedfor the purpose ofcomparing the'fluid loss properties of'chrome' lignin gels, which'were prepared as aforesaid and-to whichvarying amounts of filter aid materials wereadded; For these tests, a Baroid filter press was employed and the measure- 7 ments were made following generally the procedure of the;

API code for testing drilling muds.

The results of these tests are shown in'TableL. l 1

Table I I Sample No. Filter Aid Amount Fluid Loss 7 a V grams 1.. None* None 53 TEL-30 min.

hole drilled by the air or gas method, theproperingre'dicuts for the temperature condition existingat the formae then the'solution isplaced opposite the formation by any tion will be fractured.

After the formation accepts a suificient amount of treating fluid and the gelation has occurred in the formation, at least 30 minutes should elapse before continuing drilling operations. Any gelled material in the tubing or drill pipe can easily be removed by pumping. The gelled material in the formation seals the Water producing pores and is of sufiicient strength to hold back the Water behind the gelled seal.

It should be readily apparent that applicant has devised a novel composition of matter adapted to shut off the production of Water in a bore hole drilled by the air or gas method.

The use of the novel composition is not limited to shutting off water as described above. It Will be readily apparent to those skilled in the art that the material can be injected into any porous formation or into fissures and thereby seal off the same. It is also apparent that equivalent materials, methods, and applications may be employed without departing from the spirit of the invention and the appended claims.

What is claimed is:

1. In a method of treating an earth formation with a treating composition containing gel-forming constituents selected from the group consisting of water-soluble polymerizable materials and chrome lignin materials, the step of adding to said composition a finely divided water inert filter aid material in sufficient quantity to substantially increase the fluid loss of said composition into the formation to be treated.

2. The invention as claimed in claim 1 wherein said treating composition is a gel-forming composition consisting essentially of a sodium silicate solution, and a gelling agent for said solution.

3. The invention as claimed in claim 1 wherein said treating composition is a gel-forming composition consisting essentially of lignin liquor and chromic acid.

4. The invention as claimed in claim 1 wherein said treating composition is a treating fluid having a pH in the range of 7 to 12, the essential ingredients of said fluid being a solution in water of a polymerizable mixture comprising about 95% acrylarnide and N,N- methylenebisacrylamide and a catalyst.

5. The method of sealing off an underground formation penetrated by the bore of a well Which comprises the steps of introducing into the Well bore a gel-forming composition containing a finely divided, Water inert filter aid material in sufficient quantity to substantially increase the fluid loss of the composition into the formation; placing the composition opposite the formation to be sealed off; exerting suificient pressure to inject at least a portion of the composition into said formation; and maintaining pressure on the composition until gelation thereof occurs in said formation.

6. The invention as claimed in claim 5 including the step of forming a permeable filter cake of said filter aid material on said Well bore as said composition is injected into said formation.

7. The method of claim 5, wherein said gel-forming composition comprises a dispersion of a chrome lignin material. I

8. The method of claim 5, wherein said gel-forming composition comprises a sodium silicate material.

9. The method of claim 5, wherein said gel-forming composition comprises a Water soluble polymerizable mixture.

10. The method of sealing off an underground formation penetrated by the bore of a well, which comprises the steps of introducing into the well bore an aqueous treating composition containing gel-forming constituents and containing a finely divided, water inert filter aid material in sufiicient quantity to substantially increase the fluid loss of the composition into the formation; placing the composition opposite the formation to be sealed off; exerting sutficient pressure to inject at least a portion of the composition into said formation; and maintaining pressure on the composition until gelation thereof occurs in said formation.

11. The method as defined in claim 5, wherein said gel-forming constituents comprise a water soluble polymerizable mixture, and including the step of forming a permeable filter cake of said filter aid material on said Well bore as said composition is injected into said formation.

References Cited in the file of this patent UNITED STATES PATENTS 2,131,338 Vail Sept. 27, 1938 2,176,266 Malmberg Oct. 17, 1939 2,328,625 Doran et a1. Sept. 7, 1943 2,585,378 Farris Feb. 12, 1952 2,683,690 Armentrout July 13, 1954 2,874,545 Twining Feb. 24, 1959 2,940,729 Rakowitz June 14, 1960 

1. IN A METHOD OF TREATING AN EARTH FORMATION WITH A TREATING COMPOSITION CONTAINING GEL-FORMING CONSTITUENTS SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE POLYMERIZABLE MATERIALS AND CHROME LIGNIN MATERIALS, THE STEP OF ADDING TO SAID COMPOSITION A FINELY DIVIDED WATER INERT FILTER AID MATERIAL IN SUFFICIENT QUANTITY TO SUBSTANTIALLY INCREASE THE FLUID LOSS OF SAID COMPOSITION INTO THE FORMATION TO BE TREATED. 